mrf89xa Microchip Technology Inc., mrf89xa Datasheet - Page 69

• Manufacturer Part Number: mrf89xa
• Description: Ultra-low Power, Integrated Ism Band Sub-ghz Transceiver
• Manufacturer: Microchip Technology Inc.

3.4.7.3
The dynamic range of the RSSI is more than 70 dB,
extending from the nominal sensitivity level. The IF
gain, set by the IFGAIN<1:0> bits (DMODREG<1:0>),
is used to achieve this dynamic range.
FIGURE 3-9:
3.4.7.4
The MRF89XA can be used to detect a RSSI level
above a preconfigured threshold. The threshold is set
using RTIVAL<7:0> bits (RSTHIREG<7:0>) and the
IRQ status stored in the RIRQS bit (FTPRIREG<2>),
which is cleared by writing a ‘1’.
FIGURE 3-10:
© 2010 Microchip Technology Inc.
180
160
140
120
100
80
60
40
20
0
-120
RSSIVAL<7:0>
Dynamic Range
RSSI IRQ Source
RIRQS
RSSI DYNAMIC RANGE
RSSI IRQ TIMINGS
-100
24
IF_Gain = 00
26
27
-80
30
IF_Gain = 01
25
RSSI Response
Preliminary
20
Pin [dBm]
20
-60
Clear interrupt
The RSSI response versus the input signal is indepen-
dent of the receiver filter bandwidth. However, in the
absence of any input signal, the minimum value directly
reflects upon the noise floor of the receiver, which is
dependant on the filter bandwidth of the receiver.
Figure 3-9 illustrates the RSSI Dynamic Range
Response.
An interrupt can be mapped to the IRQ0 or IRQ1 pins
through the IRQ0RXS<1:0> and IRQ1RXS<1:0> bits
(FTXRXIREG<7:6>
Figure 3-10 illustrates the timing diagram of the RSSI
interrupt
(RSTHIREG<7:0>) set to ‘11100’.
20
IF_Gain = 10
18
source,
22
-40
33
IF_Gain = 11
20
with
and
22
the
MRF89XA
-20
34
FTXRXIREG<5:4>).
RTIVAL<7:0>
33
DS70622B-page 69
0
bits